Self Assessment Tax Returns

What Happens If I File My Tax Return Late?

Keeping on top of your tax return deadlines is important. If a Self Assessment tax return is filed late, HMRC can charge penalties even if you have no tax to pay, are due a refund, or have already paid the tax that was due.

The good news is that if you have missed a deadline, there are steps you can take. Filing your return as soon as possible will stop further daily late-filing penalties from accumulating. In some circumstances, you may also be able to appeal a penalty if you have a reasonable excuse.

When Is My Tax Return Due?

For most Self Assessment taxpayers, the normal filing deadlines are:

• 31 October following the end of the tax year for a paper tax return.

• 31 January following the end of the tax year for an online tax return.

For example, the online return for the tax year ending 5 April 2026 is normally due by 31 January 2027.

These are the standard deadlines. Different arrangements can apply in certain circumstances, such as when HMRC issues a notice to file after 31 July.

It is worth remembering that the filing deadline applies whether or not you have any tax to pay.

What Happens If My Tax Return Is Late?

HMRC's late-filing penalties can increase the longer a return remains outstanding.

£100 initial penalty

A £100 fixed penalty is normally charged as soon as the filing deadline is missed.

This can apply even if:

• You have no tax to pay.

• Your return shows that you are due a refund.

• You have already paid all the tax due.

£10 a day after three months

If your return is still outstanding more than three months after the deadline, HMRC can charge £10 per day, for up to 90 days.

This means the daily penalties can add up to £900.

These daily penalties stop accumulating once the return has been filed, although penalties already incurred will still need to be dealt with.

Further penalties after six and twelve months

If the return remains outstanding:

• After six months: a further penalty of the greater of £300 or 5% of the tax liability can normally apply.

• After twelve months: another penalty of the greater of £300 or 5% of the tax liability can normally apply.

Higher penalties can apply in certain circumstances, particularly where information has deliberately been withheld from HMRC.

Even a nil-tax return can result in penalties

One common misconception is that there is no penalty if there is no tax to pay.

That isn't necessarily the case.

For example, where a return is more than twelve months late and there is no tax liability, the standard late-filing penalties can potentially total £1,600, assuming the maximum daily penalties apply:

• £100 initial penalty.

• Up to £900 in daily penalties.

• £300 after six months.

• £300 after twelve months.

This is why it is important to file your return on time, even if you think you have nothing to pay.

Late Payment of Tax

Late filing and late payment are two separate matters.

If you have tax to pay and do not pay it by the relevant deadline, HMRC can charge late-payment penalties as well as interest.

Under the standard Self Assessment late-payment penalty regime, the penalties are generally:

• 5% of the tax unpaid after 30 days.

• A further 5% after six months.

• A further 5% after twelve months.

These penalties are calculated on the tax that remains unpaid at the relevant penalty dates. Interest may also be charged on tax that is paid late.

This means that someone who both files their return late and pays their tax late could potentially face penalties under both regimes.

What If I Can't Pay My Tax Bill?

If you are worried that you will not be able to pay your tax bill in full, don't ignore it.

Depending on your circumstances, you may be able to arrange a Time to Pay agreement with HMRC, allowing you to spread your payments over an agreed period.

The sooner you deal with the situation, the more options you are likely to have. We can help you understand your position and, where appropriate, assist with dealing with HMRC.

Can I Appeal a Late Filing Penalty?

Sometimes circumstances arise that make it difficult or impossible to meet a tax return deadline.

If you have a reasonable excuse for filing your return late, you may be able to appeal the penalty.

HMRC considers appeals based on the circumstances of each case, so it is important to explain clearly what happened and what you have done to put matters right.

You will usually need to appeal within 30 days of the date on the penalty notice. If you miss this deadline, you should explain why your appeal is late.

If you have received an HMRC penalty and are unsure whether you have grounds for an appeal, we can help you consider your options.

Don't Leave a Late Tax Return Until Tomorrow

If you have missed your Self Assessment deadline, don't panic — but don't put it off either.

The sooner you file the return, the sooner you can establish exactly what you owe and stop further daily late-filing penalties from accumulating.

At Dunelm, we can help with:

• Late Self Assessment tax returns.

• HMRC penalty notices.

• Late-filing and late-payment penalties.

• Penalty appeals.

• Self Assessment tax returns.

• Tax calculations.

• General tax advice and planning.

We provide a friendly, professional service to individuals and businesses in Newmarket, Bury St Edmunds, Ely, Thetford, Haverhill, Cambridge and throughout East Anglia.

Need Help With a Late Tax Return?

If you have missed a deadline, received an HMRC penalty or are simply unsure what you need to do, please get in touch.

Contact Dunelm today to discuss your circumstances. We will be happy to explain how we may be able to help.

The information on this page is intended as general guidance and reflects the rules applicable at the time of review. HMRC rules, tax legislation and penalty regimes can change, and different rules may apply depending on the tax year and your individual circumstances. Please contact us for advice relating to your particular circumstances.

Last reviewed: November 2026